U.S. Pat. No. 5,469,553 describes an electronic circuit wherein power consumption is managed using a power state machine. This circuit comprises a plurality of components that can each be switched to different states, such as a reset state, a sleep state, an idle state and an active state, wherein they consume different levels of power (and have different operating capability). U.S. Pat. No. 5,469,553 provides a microprocessor and a program memory with a program to make the microprocessor support a power state machine that controls the components to switch to their different states in accordance to a state of the power state machine. In response to internal and external events the microprocessor executes event-handling programs that switch the power state machine between its different states, with the effect that the components of the circuit are switched to respective states accordingly.
Nowadays hand-held devices (HHD) have very dynamic functionality upgrades. In order to retain high system efficiency and to maximize battery life, as well as to meet stricter printed board size requirements by using high-level system integration, development of advanced and highly integrated solutions for power supply generation and battery management becomes crucial.